Funding for this site is provided by readers like you.
From thought to language
Sub-Topics

Communicating in Words


Linked
Help Link : Language gene found Link : FOXP2: To speak or not to speak? Link : "Language gene found"
Original modules
Tool : The Human Vocal Apparatus The Human Vocal Apparatus
Tool : Chomsky's Universal Grammar   Chomsky's Universal Grammar

When these studies were published in the late 1990s and the early 2000s, some mass media rushed out with reports that the “language gene” had been discovered. In reality, of course, a phenomenon such as language is far too complex to reside on a single gene. To be more accurate, the media should have talked about “a gene that might be involved in language”, and even more precisely, as regards specific language impairment, in the development of the brain structures that underlie language.

The fact is that discovering a gene is only the first step in understanding what role it plays. The subsequent steps, which inevitably require identifying the structure and function of the protein produced by this gene, generally prove longer and more arduous.

It’s as if you were trying to understand how a car works when all you had to go by was a diagram of one of its parts. No matter how much evidence you had that this diagram did indeed represent a car part, you would have no idea what the part really looked like, or what it did, or what other parts interacted with it, much less what the car as a whole did and looked like.


GENES THAT ARE ESSENTIAL FOR SPEECH

The ability of human beings to speak involves very fine motor control of the mouth and the larynx (voice box), a kind of control that other primates lack.

Research done by the American linguist Noam Chomsky in the late 1950s and early 1960s highlighted the fact that human language is universal and complex, yet children acquire it rapidly with no explicit instructions. Chomsky’s findings suggested that the human ability to speak might have genetic origins.

Around the same time, other researchers pointed out that a small number of children failed to learn to speak. They had problems in producing and identifying the basic sounds of language as well as in understanding grammar. This condition is called “specific language impairment”, and it includes all language disorders that cannot be attributed to mental retardation, autism, deafness, or any other very general causes.

Researchers also observed that specific language impairment often occurred in more than one member of the same family and was more likely to be shared by identical twins than by fraternal ones. Scientists therefore long suspected that this condition had a hereditary component, but they did not know much about the genes that were involved.

All this changed, however, after a study of a British family of Pakistani origin, known as the KE family. In this family, out of 37 members distributed across 4 generations, 15 suffered from some form of specific language impairment. This high proportion of affected individuals within the same family indicated, first of all, that this disorder might be attributed to a single gene transmitted by either parent. In addition, this gene seemed to be transmitted by the standard dominant/recessive pattern and was not located on a sex chromosome.


Genealogical tree of the KE family. Black shapes represent persons with specific language impairments. Circles represent females, and squares represent males.



The 23 pairs of human chromosomes at the time of mitosis

In 1998, scientists established a relationship between specific language impairment and a short segment of chromosome 7. Even this short segment still contained 70 genes, so analyzing them would be an arduous task. But then, as luck would have it, researchers became aware of “CS”, a young English boy who had specific language impairments but was not a member of the KE family. Because CS had a visible defect on chromosome 7, the researchers immediately focused their efforts on this defective segment of DNA. And as they expected, this gene, which they named FOXP2, turned out to be directly correlated with specific language impairment.

As in the identification of any other gene, the next step, of course, was to find out what type of protein this gene produced.


  Presentations | Credits | Contact | Copyleft